U.S. patent number 7,499,474 [Application Number 11/105,768] was granted by the patent office on 2009-03-03 for efficient harq control and channel quality feedback reporting for multicarrier systems.
This patent grant is currently assigned to Nokia Corporation. Invention is credited to Adrian Boariu, R. Thomas Derryberry, Zhigang Rong.
United States Patent |
7,499,474 |
Derryberry , et al. |
March 3, 2009 |
Efficient HARQ control and channel quality feedback reporting for
multicarrier systems
Abstract
A method comprising receiving a plurality of data packets each
associated with one of a plurality of carriers, deriving an input
bit stream indicative of the receipt of the plurality of data
packets, utilizing an output block code to convert the input bit
stream into an output bit stream, and transmitting the output bit
stream to at least one of the plurality of carriers.
Inventors: |
Derryberry; R. Thomas (Plano,
TX), Boariu; Adrian (Irving, TX), Rong; Zhigang (San
Diego, CA) |
Assignee: |
Nokia Corporation (Espoo,
FI)
|
Family
ID: |
37087388 |
Appl.
No.: |
11/105,768 |
Filed: |
April 13, 2005 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20060233127 A1 |
Oct 19, 2006 |
|
Current U.S.
Class: |
370/538;
370/333 |
Current CPC
Class: |
H04L
1/0026 (20130101); H04L 1/0041 (20130101); H04L
1/0057 (20130101); H04L 1/0073 (20130101); H04L
1/1607 (20130101); H04L 1/08 (20130101); H04L
2001/125 (20130101) |
Current International
Class: |
H04J
9/00 (20060101) |
Field of
Search: |
;370/537,538,332,333 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Advantages of CDMA2000", internet article,
www.cdg.org/technology/3g/advantages.sub.--cdma2000.asp, Sep. 1,
2004, 5 pgs. cited by other .
"Technical Overview of 1xEV-DV White Paper", .COPYRGT. 2002
Motorola, Inc., Sep. 18, 2002, 24 pgs. cited by other .
"Physical Layer Standard for cdma2000 Spread Spectrum Systems,
Release C", 3GPP2 C.S0002-C, Version 1.0, May 28, 2002, 505 pgs.
cited by other .
Derryberry, R.T. et al., "Overview of cdma2000.RTM. Revision D", 3
pgs. cited by other .
Agrawal, A., "3.sup.rd Generation CDMA Wireless Systems", Qualcomm,
Jan. 5, 2000, 31 pgs. cited by other .
Brouwer, A.E. et al., "An Updated Table of Minimum-Distance Bounds
for Binary Linear Codes", .COPYRGT. 1993 IEEE, 16 pgs. cited by
other .
Control Channel Design for High Speed Downlink Shared Channel for
3GPP W-CDMA, Rel-5, A. Ghosh et al., Vehicular Technology
Conference, 2003, VTC 2003-Spring. The 57.sup.th IEEE Semiannual,
vol. 3, pp. 2085-2089, Apr. 2003. cited by other .
"Physical Layer Standard for cdma2000 Spread Spectrum
Systems--Revision 3", 3GPP2 Standard C.S0002-C Physical Layer
Standard for cdma2000 Spread Spectrum Revision C. Version 2.0, Jul.
2004. cited by other.
|
Primary Examiner: Urban; Edward
Assistant Examiner: Haroon; Adeel
Attorney, Agent or Firm: Harrington & Smith, PC
Claims
What is claimed is:
1. A method comprising: receiving at a wireless receiver at least
one data packet from each of a plurality of carriers in a wireless
communications system wherein communication operations are
performed between users; deriving an input bit stream indicative of
an attribute of said at least one data packet from each of said
plurality of carriers, wherein the input bit stream comprises
information to be used in controlling communication operations
involving at least one user of the wireless communications system;
deriving an output block code from a first block code, wherein
deriving means selecting output codes from the first block code,
wherein the output codes are each respectively associated with a
particular input code, and assigning the output codes from the
first block code to different input codes to generate the output
block code; utilizing the output block code to convert said input
bit stream into an output bit stream; and transmitting said output
bit stream to at least one of said plurality of carriers.
2. The method of claim 1 wherein said input bit stream comprises a
plurality of bits each indicative of a receipt/non-receipt of said
at least one data packet.
3. The method of claim 1 wherein said input bit stream comprises a
plurality of bits each indicative of a signal quality of an
individual one of said plurality of carriers.
4. The method of claim 1 wherein said first block code comprises a
1.times.EV-DV block code.
5. The method of claim 4 wherein said 1.times.EV-DV block code
comprises a full carrier to interference ratio (C/I) report block
code.
6. The method of claim 4 wherein said 1.times.EV-DV block code
comprises a (12, 4) block code.
7. The method of claim 4 wherein said at least one data packet
comprises two data packets and said output block code comprises a
(12, 2) block code.
8. The method of claim 7 wherein said output block code is
transmitted with a repetition factor of two.
9. The method of claim 7 wherein said output block code is near
optimal.
10. The method of claim 4 wherein deriving an output block code
further comprises: appending a two digit bit stream to each of a
plurality of input codes of said output block code to form a
plurality of appended input codes; retrieving an output code of
said first block code corresponding to each of said plurality of
appended output codes; and associating each retrieved output code
with its associated input code to derive said output block
code.
11. The method of claim 10 wherein said two digit bit stream is
equal to "00".
12. The method of claim 4 wherein said at least one data packet
comprises three data packets and said output block code comprises a
(12, 3) block code.
13. The method of claim 12 wherein said output block code is
transmitted with a repetition factor of two.
14. The method of claim 12 wherein said output block code is near
optimal.
15. The method of claim 4 wherein deriving an output block code
further comprises: appending a bit to each of a plurality of input
codes of said output block code to form a plurality of appended
input codes; retrieving an output code from said first block code
corresponding to each of said plurality of appended output codes;
and associating each retrieved output code with its associated
input code to derive said output block code.
16. The method of claim 15 wherein said bit is equal to "0".
17. An apparatus comprising: a signal processor configured to be
coupled to a receiver that is configured to receive a plurality of
data packets over a plurality of carriers, said signal processor
configured to derive an input bit stream indicative of an attribute
of said plurality of data packets, wherein the input bit stream
comprises information to be used in controlling communication
operations in the wireless communications system involving the
apparatus; to derive an output block code from a first block code,
wherein to derive means to select output codes from the first block
code, wherein the output codes are each respectively associated
with a particular input code, and to assign the output codes from
the first block code to different input codes to generate the
output block code; to utilize the output block code to convert said
input bit stream into an output bit stream; and to send the output
bit stream to a transmitter that is configured to transmit said
output bit stream to said plurality of carriers.
18. The apparatus of claim 17 wherein said apparatus comprises at
least one of a cellular telephone, a personal digital assistant
(PDA), a portable computer, an image capture device such as a
digital camera, a gaming device, a music storage and playback
appliance, and an Internet appliance permitting Internet access and
browsing.
19. The apparatus of claim 17 wherein said first block code is a
1.times.EV-DV block code.
20. The apparatus of claim 19 wherein said 1.times.EV-DV block code
comprises a full C/I report block code.
21. The apparatus of claim 19 wherein said 1.times.EV-DV block code
is a (12,4) block code.
22. The apparatus of claim 17 wherein said output block code is
optimal.
23. The apparatus of claim 17 wherein said output block code is
near optimal.
24. The apparatus of claim 17 wherein said input bit stream
comprises a plurality of bits each indicative of a
receipt/non-receipt of a unique one of said plurality of data
packets.
25. The apparatus of claim 17 wherein said input bit stream
comprises a plurality of bits each indicative of a signal quality
of a unique one of said plurality of data packets.
26. An apparatus configured for use in an electronic device, the
electronic device configured to perform communication operations
for a user in a wireless communications system, the apparatus
comprising: a signal processor configured to be coupled to a
receiver that is configured to receive a plurality of data packets,
said signal processor configured to derive an input bit stream
indicative of an attribute of said plurality of data packets,
wherein the input bit stream comprises information to be used in
controlling communications operations in the wireless
communications system involving the electronic device; to derive an
output block code from a first block code, wherein to derive means
to select output codes from the first block code, wherein the
output codes are each respectively associated with a particular
input code, and to assign the output codes from the first block
code to different input codes to generate the output block code;
and to utilize the output block code to convert said input bit
stream into an output bit stream for transmission from a
transmitter.
27. The apparatus of claim 26 wherein said first block code is a
1.times.EV-DV block code.
28. The apparatus of claim 27 wherein said 1.times.EV-DV block code
comprises a full C/I report block code.
29. The apparatus of claim 27 wherein said 1.times.EV-DV block code
is a (12,4) block code.
30. The apparatus of claim 26 wherein said output block code is
optimal.
31. The apparatus of claim 26 wherein said output block code is
near optimal.
32. A mobile station configured to perform communications
operations in a wireless communications system, the mobile station
comprising: means for receiving at least one data packet from each
of a plurality of carriers; means for deriving an input bit stream
indicative of an attribute of said plurality of data packets,
wherein the input bit stream comprises information to be used in
controlling communication operations in the wireless communications
system involving the mobile station; means for utilizing an output
block code to convert said input bit stream into an output bit
stream; and means for transmitting said output bit stream to at
least one of said plurality of carriers where said output block
code is derived from a first block code, and wherein derived means
selecting output codes from the first block code, wherein the
output codes are each respectively associated with a particular
input code, and assigning the output codes from the first block
code to different input codes to generate the output block
code.
33. The mobile station of claim 32 wherein said first block code is
a 1.times.EV-DV block code.
Description
BACKGROUND
1. Field
Embodiments of the invention relate to a method, apparatus, and
computer program product for efficiently communicating feedback in
wireless communication systems, and, more particularly, to a code
based form of communication between a single mobile station and
multiple carriers, such as may operate in a cdma2000 system or
similar systems.
2. Brief Description of Prior Developments
3.times.EV-DV represents an extension of the single carrier
1.times.EV-DV standard to a standard wherein a single mobile
station (MS) can be in simultaneous communication with one, two, or
three carriers. One advantageous attribute of 1.times.EV-DV's
robust high-speed downlink data transmission is its ability to
dynamically schedule users as a function of the user's received
channel quality. In a 1.times.EV-DV system, each mobile station is
in contact with, at most, one carrier at a time. As a result, it is
necessary to provide for the acknowledgement/non-acknowledgement of
only one received packet at a time.
The multicarrier extension of 1.times.EV-DV to 3.times.EV-DV
requires the ability of each MS to acknowledge/non-acknowledge
(ACK/NAK), via the reverse acknowledgement channel (R-ACKCH), up to
three received packets simultaneously.
With reference to FIG. 1, there is illustrated a representative
scenario for the spectral relationships of the forward and reverse
links of 3.times.EV-DV used by three nodes and a mobile station.
The forward link component of 3.times.EV-DV is shown in exemplary
fashion as employing three forward link spectra 21, 21', 21'' for
forward communication from a node such as a base station to a MS.
Each forward link spectrum 21, 21', 21'' is generally symmetric
about a downlink frequency. As used herein, a node may be a base
station, another MS, a LAN gateway, or any other transceiving
entity within a wireless network that communicates with the MS.
Where an entity transmits over multiple antennas, each antenna is
considered a node.
In the instance illustrated, the downlink frequencies consist of a
central downlink frequency f.sub.OD, and two additional downlink
frequencies disposed on either side of f.sub.OD, at a distance of
approximately 1.25 MHz. For the purposes of this description, it is
assumed, but not required, that the three downlink spectral bands
21, 21', 21'' are adjacent. In addition, there is shown a
1.times.EV-DV reverse link consisting of a reverse link spectrum 23
centered on an uplink frequency f.sub.OU.
As is evident, the operational bandwidths across the entire forward
link are not symmetric with the reverse link. When seeking to
extend the existing 1.times.EV-DV system to the multicarrier
3.times.EV-DV system, it would appear at first glance that one
might simply linearly extend the 1.times.EV-DV model by a factor of
three. However, it is not desirable to simply triple the reverse
link overhead, since the additional reverse link bandwidth would be
largely wasted.
What is therefore needed is a method of transmitting received
channel quality information over a reverse link from a mobile
station to another node in a 3.times.EV-DV system that does not
require a significant increase in transmission overhead beyond that
which is required for 1.times.EV-DV. Preferably, such a method
would preserve compatibility with preexisting 1.times.EV-DV
systems. In addition, such a methodology should be extendable to
providing for the transmission of multiple data streams from a MS
to one or more carriers, such as data streams used to transmit
signal quality information. Further, such a technique would
minimize, to the extent possible, impact to existing reverse link
protocol.
SUMMARY
In accordance with one aspect of the present invention, a method is
provided comprising receiving a plurality of data packets each
associated with one of a plurality of carriers, deriving an input
bit stream indicative of the receipt of the plurality of data
packets, utilizing an output block code to convert the input bit
stream into an output bit stream, and transmitting the output bit
stream to at least one of the plurality of carriers.
In accordance with another aspect of the present invention, a
multi-carrier wireless communication system comprises a plurality
of carriers each transmitting a plurality of data packets, and a
mobile station in communication with each of the plurality of
carriers for receiving the plurality of data packets, deriving an
input bit stream from the plurality of received data packets,
utilizing an output block code to convert the input bit stream into
an output bit stream, and transmitting the output bit stream to the
plurality of carriers.
In accordance with another aspect of the present invention, a
program of machine-readable instructions, tangibly embodied on an
information bearing medium and executable by a digital data
processor, to perform actions directed toward communicating
feedback in communication systems, the actions comprise receiving
data packets from each of a plurality of carriers, deriving an
input bit stream indicative of the receipt of the plurality of data
packets, utilizing an output block code to convert the input bit
stream into an output bit stream, and transmitting the output bit
stream to at least one of the plurality of carriers.
In accordance with another aspect of the present invention, a
method comprises a step for receiving data packets from each of a
plurality of carriers, a step for deriving an input bit stream
indicative of the receipt of the plurality of data packets, a step
for utilizing an output block code to convert the input bit stream
into an output bit stream, and a step for transmitting the output
bit stream to at least one of the plurality of carriers.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing aspects and other features of the present invention
are explained in the following description, taken in connection
with the accompanying drawings, wherein:
FIG. 1 is a diagram of the spectral relationship between the
forward and reverse links in a 3.times.EV-DV system.
FIG. 2 is a block diagram of the reverse acknowledgement channel
(R-ACKCH) structure for a 1.times.EV-DV system known in the
art.
FIG. 3 is a block diagram of the R-ACKCH structure for a
3.times.EV-DV system according to the present invention.
FIGS. 4(a-c) are block diagrams of examples of the R-ACKCH
structure in accordance with embodiments of the invention.
FIG. 5 is a block diagram of an R-ACKCH structure for HARQ
reporting over one or more carriers according to embodiments of the
invention.
FIG. 6 is a diagram of a single MS in a 3.times.EV-DV system
receiving over three forward links and transmitting over one
reverse link.
FIG. 7 is a block diagram CQICH structure for handling one or more
carrier channel quality reporting according to embodiments of the
invention.
FIG. 8 is a block diagram of an alternative example of the CQICH
structure for handling one or more carrier channel quality
reporting according to embodiments of the invention.
FIG. 9 is a block diagram of an alternative example of the CQICH
structure for handling one or more carrier channel quality
reporting according to embodiments of the invention.
FIG. 10 is a block diagram of an example of the R-CQICH structure
for handling one or more carrier C/I reporting according to
embodiments of the invention.
DETAILED DESCRIPTION
An example of the present invention provides for acknowledging an
attribute of data packets received over multiple carriers
including, but not limited to, receipt/non-receipt, signal quality,
and channel quality. This is achieved by employing a block code
derived in part from an existing 1.times.EV-DV block code
definition. As used herein "1.times.EV-DV block code" refers to
block code defined in the standards for 1.times.EV-DV systems, such
as at "Physical Layer Standard for cdma2000 Spread Spectrum Systems
Release C", 3GPP2 Document No. C.S0002-C V1.0, May 28, 2002
(hereinafter "the standard") which is herein incorporated by
reference. As is described more fully below, by eschewing simple
repetition in favor of a block code derived from an existing
standard, transmission overhead is reduced and error detection is
enhanced in comparison to a linear extension of 1.times.EV-DV to
3.times.EV-DV. In addition, utilization of an existing
1.times.Ev-DV standard, such as disclosed in table 2.1.3.1.4.3-1 of
the standard, maintains backwards compatibility from a
3.times.EV-DV system to that of 1.times.EV-DV.
With reference to FIG. 2, there is illustrated the reverse
acknowledgement channel (R-ACKCH) as implemented presently in
1.times.EV-DV systems. The acknowledgements sent on the R-ACKCH at
block 31 indicate whether or not a mobile station received a packet
correctly. In typical operation, this reverse link ACK/NAK
reporting is enabled through the use of a single bit sent by the MS
over the R-ACKCH. MSs can include, but are not limited to, cellular
telephones, personal digital assistants (PDAs), portable computers,
image capture devices such as digital cameras, gaming devices,
music storage and playback appliances, Internet appliances
permitting Internet access and browsing, as well as portable units
or terminals that incorporate combinations of such functions. In
order to insure receipt of the acknowledgement, the bit may be
repeated numerous times. In the present example the symbol
repetition is set to a factor of 24 at step 33. As noted, a
straightforward linear extension from 1.times.EV-DV to
3.times.EV-DV would involve the tripling of the associated overhead
from 24 bits to 72 bits.
In FIG. 2, a single ACK/NACK bit for the single forward link is
mapped to a symbol and repetition of the symbol on the reverse link
equates to repetition of the ACK/NACK bit.
With reference to FIG. 6 there is illustrated the flow of data from
three separate transmit antennas 63, 63', 63'' to a mobile station
61 and back via reverse link 67 acting as the R-ACKCH according to
the present invention. Data packets are sent by the nodes 63, 63',
63'' to the MS 61 via forward links 65, 65', 65''. In return, the
MS 61 constructs a bit stream consisting of one bit for each node
63 with which the MS 61 is in communication indicating whether or
not a data packet sent by one or more nodes 63 was correctly
received. For example, the MS 61 may construct a stream of "0,1,1"
indicating that a first node's data packet was not received without
error while a second and a third node's data packets were received
without error.
The information contained in the bit stream forms the basis of the
output bit stream that is transmitted by the MS 61 to the nodes 63,
63', 63'' via reverse link 67. As will be discussed below, the
output bit stream is preferably formed from an output block code,
which may or may not be repeated. In a preferred, but non-limiting
example, the block code is derived from an existing 1.times.EV-DV
block code. By "derived", it is meant that each output code in the
output block code is an output code in the 1.times.EV-DV block
code, but which is associated with a similar, but different, input
code.
With reference to FIG. 3, there is illustrated the R-ACKCH as
implemented in a 3.times.EV-DV system resulting from a linear
extension of 1.times.EV-DV. The exemplary depiction shows how to
achieve hybrid automatic repeat requests (HARQ) reports for data
packets received on each of a multitude of carriers. In the present
case, three carriers are assumed. As such, symbol repetition is set
to a factor of 8 (24 bits/3 carriers=8 symbols/carrier). The
extension of the solution illustrated to the case where, for
example, two carriers are enabled on downlink is similar.
Such an implementation of the R-ACKCH in a 3.times.EV-DV system
serves to maintain backwards compatibility with 1.times.EV-DV
systems. One drawback of such a reduced repetition approach
(reduced from a factor of 24 to a factor of 8) is the reverse link
power overhead required. Specifically, as the bit repetition factor
is reduced, more transmit power is required from the MS to maintain
reliability.
As noted above, the present invention teaches a method of
performing R-ACKCH in a 3.times.EV-DV system which does not incur a
linear increase in overhead as a result of moving from a 1.times.
to a 3.times. system and which enables R-ACKCH communication in a
manner that is more efficient than employing symbol repetition.
This is achieved through the implementation of an output block code
the use of which enables the MS 61 to acknowledge the
receipt/non-receipt of more than one data packet at a time.
In general, use of symbol repetition as discussed above can be
thought of as a simple block code. The performance of block codes
is directly tied to the minimum Hamming distance amongst all of the
codes forming the block code. The Hamming distance of any two codes
is equal to the number of positions in bit sequences where the bits
of the output codes are different. For example, the two bit
sequences `1 0 1 1 0 0 1` and `1 1 0 0 1 0 1` have a Hamming
distance of four. For the case of transmitting one bit that is
repeated N times as depicted in FIGS. 2 and 3, the Hamming distance
is N (Either N 1's or N 0's are the transmission sequence for the
two possible cases).
When seeking to insure correct receipt of a coded message, such as
a R-ACKCH communication, in an environment where corruption of the
message is possible, one desires to use a code block with as large
a Hamming distance as possible. The larger the Hamming distance,
the greater the likelihood that a corrupted received data stream
can be correctly resolved to the originally transmitted
message.
Consider, for example a code block formed of four bit output codes,
where each output code represents a number between zero and fifteen
(binary 0000 and 1111 respectively). Such a block code has a
minimum Hamming distance of one. That is to say, each output code
differs from its next most similar output code by only one bit.
Further consider the transmission by a MS of the code for "7"
(0111) which is corrupted by one bit to read "5" (0101). Such a
corruption results in the transformation of the originally sent
code into another legitimate code sequence. As such, there is no
way to determine from the received packet data if the data received
is corrupted, and, if so, what the original message was.
As the minimum Hamming distance of a code block increases, so does
the accuracy of transmitted data in the presence of corruption.
Consider a block code with a minimum Hamming distance of ten. If
one bit is corrupted in a received code, the received code differs
from a legitimate code by one bit and the next most similar
legitimate code by nine bits. It is therefore most probable that
the transmitted code was the code which differs by only one
bit.
Consider the block code used in defining the 1.times.EV-DV full C/I
report as depicted in Table 1 (table 2.1.3.1.4.3-1 of the
standard):
TABLE-US-00001 TABLE 1 Codewords for the Reverse Channel Quality
Indicator Channel (12, 4) Block Code Input Output `0000` `0000 0000
0000` `0001` `0101 0101 0101` `0010` `0011 0011 0011` `0011` `0110
0110 0110` `0100` `1111 0000 1111` `0101` 1010 0101 1010` `0110`
`1100 0011 1100` `0111` `1001 0110 1001` `1000` `0000 1111 1111`
`1001` `0101 1010 1010` `1010` `0011 1100 1100` `1011` `0110 1001
1001` `1100` `1111 1111 0000` `1101` `1010 1010 0101` `1110` `1100
1100 0011` `1111` `1001 1001 0110`
A block code represents an input bit stream (input code) of length
X and an associated output bit stream (output code) of length Y.
Block codes may be referred to by the format (Y,X). The block code
of Table 1 is therefore a (12,4) block code. Note that the minimum
Hamming distance for this block code is six.
Table 2 depicts exemplary code words for the 3.times.EV-DV HARQ
reports using bit repetition coding as defined in FIG. 3:
TABLE-US-00002 TABLE 2 Code words for the Reverse Acknowledgement
Channel as defined in FIG. 3 (3 bit input denotes 3 carrier
reporting). Input Output `000` `0000 0000 0000 0000 0000 0000`
`001` `0000 0000 0000 0000 1111 1111` `010` `0000 0000 1111 1111
0000 0000` `011` `0000 0000 1111 1111 1111 1111` `100` `1111 1111
0000 0000 0000 0000` `101` `1111 1111 0000 0000 1111 1111` `110`
`1111 1111 1111 1111 0000 0000` `111` `1111 1111 1111 1111 1111
1111`
Specifically, Table 2 shows every possible three-bit combination as
an input code and an output code formed from repeating each bit in
the input code by a factor of eight. Note that in this case,
repetition occurs over a vector of input bits, but does not
preclude repetition of each of the input bits individually. Observe
that the minimum Hamming distance for this code is eight.
Similarly, for two carrier reporting utilizing N=12 repetition, the
minimum Hamming distance is twelve. One may denote the three
carrier differential reporting code in Table 2 as a (24,3) block
code and the two carrier differential reporting code as a (24,2)
block code.
The theoretical minimum, hence optimal, Hamming distances for the
(24,3) and (24,2) linear codes can be mathematically computed to be
thirteen and sixteen, respectively. Therefore, utilization of
simple repetition for two and three carrier HARQ reporting as
illustrated above is not optimal.
The present invention provides a method for deriving a (24,3) and
(24,2) block code for use in HARQ reporting which, in each
instance, results in a near optimal or optimal minimum Hamming
distance. As used herein, "near optimal" refers to a block code
with a minimum Hamming distance less than the theoretically
computed optimal Hamming distance but which is greater than is
obtained through mere repetition.
While illustrated herein with reference to output block codes
having output codes each a multiple of twelve, the examples of the
present invention are not so limited. Rather the examples of the
invention encompass the derivation of output block codes having
output code lengths which are integer multiples of the output code
lengths of conventional, e.g., 1.times.EV-DV block codes.
The derivation proceeds as follows. Denote the 4 bit input sequence
used in 1.times.EV-DV systems and illustrated in Table 1 as
x.sub.1,x.sub.2,x.sub.3,x.sub.4. The goal is to take the (12,4)
linear code and derive an optimal (24,3) linear code that has a
minimum Hamming distance of 13 (the computed theoretical limit).
For the case of three HARQ reports, one such near optimal code
results from selecting the codeword corresponding to a "0" being
appended to the three bit HARQ report and repeat it. For example,
the corresponding codeword of a three carrier HARQ report of "101"
would be `0011 1100 1100 0011 1100 1100`, which corresponds to the
entry 1010 in Table 1 and which is repeated vector-wise. While the
(12,4) code of Table 1 utilized to create the output block code of
the present invention is comprised of the code words defined for
the reverse channel quality indicator channel for a 1.times.EV-DV
system (a 1.times.EV-DV block code), any such standard block code
may be used that results in an optimal or near optimal output block
code.
Table 3 depicts two different near optimal (24,3) linear codes,
differentiated by a version number, derived from the (12,4) code
defined in Table 1.
TABLE-US-00003 TABLE 3 Codewords for the Reverse Acknowledgement
Channel for the (24, 3) Block Code (Two near optimal (24, 3) codes
derived from the optimal (12, 3) code shown). Input Output Version
`000` `0000 0000 0000 0000 0000 0000` 1 `000` `0101 0101 0101 0101
0101 0101` 2 `001` `0011 0011 0011 0011 0011 0011` 1 `001` `0110
0110 0110 0110 0110 0110` 2 `010` `1111 0000 1111 1111 0000 1111` 1
`010` `1010 0101 1010 1010 0101 1010` 2 `011` `1100 0011 1100 1100
0011 1100` 1 `011` `1001 0110 1001 1001 0110 1001` 2 `100` `0000
1111 1111 0000 1111 1111` 1 `100` `0101 1010 1010 0101 1010 1010` 2
`101` `0011 1100 1100 0011 1100 1100` 1 `101` `0110 1001 1001 0110
1001 1001` 2 `110` `1111 1111 0000 1111 1111 0000` 1 `110` `1010
1010 0101 1010 1010 0101` 2 `111` `1100 1100 0011 1100 1100 0011` 1
`111` `1001 1001 0110 1001 1001 0110` 2
Note that these two (24,3) codes have a minimum Hamming distance of
twelve, which is very close to the optimal minimum achievable
distance of thirteen and greater than the Hamming distance of eight
for the code defined in Table 2. Also note the codes are defined by
selecting the input codeword from the (12,4) block code of Table 1
by appending either a "0" or a "1" as x.sub.4 to the 3 bit HARQ
report to derive an output code (this yields the optimal (12,3)
code) and repeating by a factor of 2. Specifically, inputs having a
version "1" correspond to appending a "0" as x.sub.4 to the 3 bit
HARQ report of Table 2. Conversely, inputs having a version "2"
correspond to appending a "1" as x.sub.4 to the 3 bit HARQ report
of Table 2.
A "proper code" is defined as a code that includes the all-zero
codeword and the binary addition of any two output codewords result
in an output codeword (linearity property). Thus the (24,3) derived
from the repeated (12,3) code corresponding to version "1" is the
preferred code since it is a proper code.
An optimal (24,2) code can be obtained in a similar fashion. Table
4 depicts four different optimal (24,2) linear codes, versions "1",
"2", "3", and "4" respectively, derived from the (12,4) code
defined in Table 1.
TABLE-US-00004 TABLE 4 Codewords for the Reverse Channel Quality
Indicator Channel Di3fferential Reports for the (24, 2) Block Code
(Four optimal (24, 2) codes derived from the (12, 2) code shown).
Input Output Version `00` `0000 0000 0000 0000 0000 0000` 1 `00`
`0101 0101 0101 0101 0101 0101` 2 `00` `0011 0011 0011 0011 0011
0011` 3 `00` `0110 0110 0110 0110 0110 0110` 4 `01` `1111 0000 1111
1111 0000 1111` 1 `01` `1010 0101 1010 1010 0101 1010` 2 `01` `1100
0011 1100 1100 0011 1100` 3 `01` `1001 0110 1001 1001 0110 1001` 4
`10` `0000 1111 1111 0000 1111 1111` 1 `10` `0101 1010 1010 0101
1010 1010` 2 `10` `0011 1100 1100 0011 1100 1100` 3 `10` `0110 1001
1001 0110 1001 1001` 4 `11` `1111 1111 0000 1111 1111 0000` 1 `11`
`1010 1010 0101 1010 1010 0101` 2 `11` `1100 1100 0011 1100 1100
0011` 3 `11` `1001 1001 0110 1001 1001 0110` 4
Note that these four (12,2) codes have a minimum Hamming distance
of 16 corresponding to the optimal minimum achievable distance.
Also note they are defined by selecting the input codeword from the
(12,4) code in Table 1 by appending a "00", "01, "10", or an "11"
as x.sub.3,x.sub.4 to the 2 bit HARQ report (this yields the
optimal (12,2) code) and repeating. The (24,2) code corresponding
to version "1" in Table 4 is the preferred code since it is a
proper code. It should be noted that the (24,2) code is composed of
a repetition of the optimal (12,2) code.
The advantages of the (24,3) and (24,2) output block codes are
several. They are either optimal (as in the (24,2) case) or near
optimal (as in the (24,3) case) and exhibit improved Eb/No
performance when compared to using only repetition. Further, they
may be derived from a pre-existing code library already in use in
existing 1.times.EV-DV systems, thus simplifying
implementation.
With reference to FIG. 4, there are illustrated three examples
depicting the R-ACKCH channel structure for three carrier HARQ
reporting making use of the near optimal (24,3) linear code. With
reference to FIG. 4a, there is illustrated an example wherein the
three reverse acknowledgement channel bits are communicated via the
near optimal (24,3) block code of Table 2. With reference to FIG.
4b, there is illustrated an alternative example wherein the three
reverse acknowledgement channel bits are communicated via an
optimal (12,3) block code repeated by a factor of two. Lastly, with
reference to FIG. 4c, there is illustrated an alternative example
wherein there is appended either a "0" or a "1" to the three
reverse acknowledgement channel bits to produce an input to the
(12,4) block code of Table 1, whereby the (12,4) block code output
is transmitted using a repetition factor of two. It is further
evident that FIG. 4 can be modified to incorporate the optimal
(12,2) linear code for two carrier HARQ reporting. Note that
repetition of the output can be done bitwise or any other pattern,
not only vectorwise as illustrated in FIGS. 3 and 4.
With reference to FIG. 5, there is illustrated a block diagram of a
logical structure for handling HARQ reporting in the 1, 2, and 3
bit input scenarios. A first selector 51 serves to decide which
block code methodology will be employed based upon the number of
input reverse acknowledgement channel bits. If the number of input
bits is one, the input bit is repeated a total of twenty-four times
(block 54). If the number of input bits is three, a "0" or a "1"
("0" preferred) is appended to the input code (block 52) to derive
the output of the optimal (12,4) block code (block 58) which is
then communicated with a repeat factor of two (block 55). Lastly,
If the number of input bits is two, a "00", "01", "10", or "11"
("00" preferred) is appended to the input code (block 56) to derive
the output of the optimal (12,4) block code (block 57) which is
then communicated with a repeat factor of two (block 55'). A second
selector 53 then communicates the appropriate output bit stream via
the reverse link.
In an alternative example of the present invention, use of the
1.times.EV-DV block code of Table 1 can be utilized to allow a MS
to report on the channel quality of a multitude of carriers. As
before, the extension from transmitting information over a reverse
link in a 1.times.EV-DV system to a 3.times.EV-DV scenario is
accomplished without tripling the overhead.
In present 1.times.EV-DV systems, MSs report pilot strengths, e.g.
C/I, to the network in which they operate. The design of the
1.times.EV-DV reverse channel quality channel (R-CQICH) allows the
MS to perform fast reporting of the best-received pilot strength
and identify the source of the best pilot with a sector specific
Walsh cover. The fast reporting can be accomplished in two
different ways: 1) Full rate mode which consists of reporting the
C/I every 20 ms with differential reports every 1.25 ms in between
full reports, or 2) Reduced rate mode which consists of the C/I
being repeated over multiple 1.25 ms intervals, and differential
C/I updates sent over the remaining 1.25 ms slots in each 20 ms
period. This scheme works quite well for the single carrier case
experienced in 1.times.EV-DV systems. The present invention
provides a method for extending R-CQICH reporting to 3.times.EV-DV
systems without a linear expansion in overhead.
Consider the periodic full C/I report made for 1.times.EV-DV and
its application/extension to the 3.times. multi-carrier case. It is
very likely the channel fading is highly correlated in the 3.times.
multi-carrier case since the assumed downlink bandwidth of 5 Mhz is
smaller than the channel coherence bandwidth. Hence the full C/I
report can be derived as the average of the carriers' corresponding
C/I's. Just performing this extension (average C/I reporting) would
achieve backwards compatibility assuming nothing else was changed
in the design. Stated another way, the differential reports would
provide differential updates to the average received C/I observed
by the MS. However, this approach does not make use of the
differential data available for each individual carrier.
The best approach to facilitate more aggressive scheduling on the
forward link would be to incorporate C/I reporting for each
carrier, but this would create three times the overhead in the
reverse link thus reducing the usable reverse link data carrying
capacity. A more efficient approach would be to report the average
C/I coupled with differential reports where each differential
update reflects the deviation of the received signal strength for
each carrier with respect to the average received signal
strength.
With reference to FIG. 7, there is illustrated an example for
achieving differential C/I reports for each carrier with respect to
the average received C/I at the MS according to the present
invention. The Average CQI Update 71 is typically a four bit number
representing a level from zero to fifteen corresponding to the
instantaneous average channel quality amongst all of the carriers
in communication with the mobile station. The Average CQI Update is
periodically transmitted from the MS to one or more carriers via
the reverse link. The Differential CQI 73 Update is a string of
one, two, or three bits corresponding to the number of carriers
with which the MS is in contact in a 3.times.EV-DV system.
The telecommunications system assigns specific CQI covers for each
sector or cell within the telecommunications system. The CQI cover
is used by the mobile station to inform the network for which
sector or cell of the telecommunications system the CQI report is
valid. The CQI cover also indicates to the telecommunications
network which sector or cell the mobile station prefers to receive
downlink transmissions from the telecommunications system.
With reference to FIG. 8, there is illustrated another example of
the present invention. In the present example, the Differential CQI
Update for a three carrier scenario is formed by appending a "0" or
a "1" to a three bit symbol and utilizing a (12,4) block code as
described above. With reference to FIG. 9, there is illustrated an
example wherein the Differential CQI Update for a three carrier
scenario is formed from a three bit symbol and is transmitted using
a (12,3) block code as described above.
With reference to FIG. 10, there is illustrated a diagram of an
example wherein differential C/I reporting is achieved for each of
one or more carriers with respect to the average received C/I at
the MS according to the present invention. In the instance that the
Differential CQI symbol is formed of a single bit, the Differential
CQI symbol is transmitted with a symbol repetition of twelve. If
the Differential CQI symbol is formed of more than one bit, bits
are appended to the Differential CQI symbol as described above so
as to facilitate the transmission of the Differential CQI Update
using a (12,4) block code.
In between transmission of the Average CQI Update 1001, one or more
Differential CQI Updates are sent by the MS to indicate, for each
carrier, whether the carrier's signal strength has increased (bit
equal to "1") or decreased (bit equal to "0"). For example, the bit
sequence "0, 1, 1" indicates that the signal quality of a first
carrier has decreased while that of the two remaining carriers has
increased. While illustrated with a bit value of "1" indicating an
increase in strength and a bit value of "0" indicating a decrease
in signal strength, the values could in practice be reversed.
Differential CQI Updates 1002 consisting of two, or three, can be
sent at any desired interval using the optimal (12,4) block code of
Table 1 to derive an optimal or near optimal output block code for
producing an output bit stream to be transmitted to one or more
carriers in a manner similar to that described above with reference
to R-ACKCH communication. As before, a repetition factor may be
utilized as desired. Average CQI Updates consisting of four bits
can be transmitted using the optimal (12,4) block code of Table 1
without the need for appending a one or two digit bit code to the
input code so as to derive an output block code.
As described herein, each MS is configured to operate as an element
in a multi-carrier wireless network such that it is capable of
receiving data packets from one or more carriers, creating any of a
multitude of input bit streams containing data, utilizing a block
code to convert the input bit streams into at least one output bit
stream, and transmitting the output bit stream. Similarly, each
carrier is capable of receiving and decoding the transmitted output
stream to obtain the original input bit stream. As noted, because
existing MSs and carriers presently perform operations involving
the 1.times.EV-DV block code of Table 1, the carriers are able to
efficiently perform such decoding. In many cases, specialized
hardware in each carrier is devoted to such decoding.
It should be understood that the foregoing description is only
illustrative of the invention. Various alternatives and
modifications can be devised by those skilled in the art without
departing from the invention. Accordingly, the present invention is
intended to embrace all such alternatives, modifications and
variances that fall within the scope of the appended claims.
* * * * *
References